Field of the Invention
The present invention relates to exposure methods and exposure apparatuses, and device manufacturing methods, and more particularly to an exposure method and an exposure apparatus by a proximity method used in a lithography process for manufacturing microdevices (electron devices) such as a semiconductor device, a liquid crystal display device and the like, and a device manufacturing method including the lithography process.
Description of the Background Art
For example, when manufacturing a semiconductor device, a liquid crystal display device, or a printed-circuit board and the like in a photolithography process, a proximity exposure apparatus is used which illuminates a photomask or a mask and the like (hereinafter collectively called a “mask”) with an exposure light and exposes a pattern of the mask onto a substrate on which a photosensitive material is coated that is placed in proximity with the mask (for example, refer to U.S. Pat. No. 5,891,806).
However, in the conventional proximity exposure apparatus, because the gap (clearance) between the pattern surface of the mask and the surface of a photosensitive layer formed on the substrate by the photosensitive material was minimally around 30 μm, resolution was poor, therefore, the conventional proximity exposure apparatus cannot possibly be used for line widths under 64 nm which is the practical minimum line width of semiconductor devices today, such as, for example, when forming a critical pattern having a line width of 32 nm on a substrate and the like.
In order to resolve a pattern having a line width under 32 nm, exposure should be performed by a double-patterning method using the latest liquid immersion type ArF scanner (scanning stepper), or by using an electron beam or an X-ray (especially an SOR light: synchrotron orbital radiation light) lithography technique.
The liquid immersion type ArF scanner which supports the double-patterning is costly. Further, the electron beam lithography can control pattern forming of a nanometer order with high precision, and also has an advantage of being able to directly draw the pattern on a wafer without using the mask. However, on the contrary, because the electron beam lithography has low throughput and is costly, the electron beam lithography has a disadvantage of still being far from the mass-production level.
Further, in the lithography using the electron beam or the X-ray, a photoresist has to be developed according to the exposure method, and there still are many problems related to sensitivity, resolution, etching resistance and the like.
Therefore, as a method for solving such problems, recently, a method of forming a fine pattern has been proposed (for example, refer to U.S. Pat. No. 6,869,732), in which a near-field light leaking out from an aperture sufficiently smaller than a wavelength of a light that is irradiated serves as a light source to perform exposure and development of the photoresist. According to this method, space resolution of a nanometer order can be obtained, regardless of the wavelength of the light source.
However, in the exposure method disclosed in, for example, U.S. Pat. No. 6,869,732, which substantially employs a contact method, although liquid intervenes between a mask and a substrate, it is actually difficult to avoid damage of the mask, decrease in yield and the like. Because conventional masks are costly, such damages have to be prevented as much as possible. In addition, in this method, because there is no projection optical system, it was difficult to cope with deformation of the mask, such as, for example, deformation of a pattern on the mask (warp, magnification change) caused by thermal deformation of the mask, and decrease in overlay accuracy could not be prevented. This point was also similar in the conventional proximity exposure apparatus.